Why rods and cones?

Lamb, Trevor D

doi:10.1038/eye.2015.236

Cited by 84 publications

(64 citation statements)

References 34 publications

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“…Our study has established new details of primate retinal wiring, but more broadly our findings are of relevance to evolutionary aspects of retinal circuitry 5 , 38 . It is known that the fundamental architecture of the retina has been dictated by cones, which are phylogenetically more ancient than rods 46 , 47 . Primordial vertebrates possessed only cone-like photoreceptors, and parallel processing of cone signals was likely established by subsets of cone bipolar and amacrine cells at the time when rods appeared 46 .…”

Section: Discussionmentioning

confidence: 99%

AII amacrine cells in the primate fovea contribute to photopic vision

Strettoi

Masri

2018

Sci Rep

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The AII amacrine cell is known as a key interneuron in the scotopic (night-vision) pathway in the retina. Under scotopic conditions, rod signals are transmitted via rod bipolar cells to AII amacrine cells, which split the rod signal into the OFF (via glycinergic synapses) and the ON pathway (via gap junctions). But the AII amacrine cell also has a “day job”: at high light levels when cones are active, AII connections with ON cone bipolar cells provide crossover inhibition to extend the response range of OFF cone bipolar cells. The question whether AII cells contribute to crossover inhibition in primate fovea (where rods and rod bipolar cells are rare or absent) has not been answered. Here, immunohistochemistry and three-dimensional reconstruction show that calretinin positive cells in the fovea of macaque monkeys and humans have AII morphology and connect to cone bipolar cells. The pattern of AII connections to cone bipolar cells is quantitatively similar to that of AII cells outside the fovea. Our results support the view that in mammalian retina AII cells first evolved to serve cone circuits, then later were co-opted to process scotopic signals subsequent to the evolution of rod bipolar cells.

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Section: Discussionmentioning

confidence: 99%

AII amacrine cells in the primate fovea contribute to photopic vision

Strettoi

Masri

2018

Sci Rep

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“…Under dark conditions, rod and cone photoreceptors exist in a constant depolarised state and continuously release glutamate [ 24 , 25 ]. However, when stimulated by light, the rod and cone photoreceptors undergo graded alterations in membrane potential and hyperpolarize, resulting in a reduction in glutamate release.…”

Section: Neuronal Basis For the Pupillary Light Reflexmentioning

confidence: 99%

Eyeing up the Future of the Pupillary Light Reflex in Neurodiagnostics

2018

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The pupillary light reflex (PLR) describes the constriction and subsequent dilation of the pupil in response to light as a result of the antagonistic actions of the iris sphincter and dilator muscles. Since these muscles are innervated by the parasympathetic and sympathetic nervous systems, respectively, different parameters of the PLR can be used as indicators for either sympathetic or parasympathetic modulation. Thus, the PLR provides an important metric of autonomic nervous system function that has been exploited for a wide range of clinical applications. Measurement of the PLR using dynamic pupillometry is now an established quantitative, non-invasive tool in assessment of traumatic head injuries. This review examines the more recent application of dynamic pupillometry as a diagnostic tool for a wide range of clinical conditions, varying from neurodegenerative disease to exposure to toxic chemicals, as well as its potential in the non-invasive diagnosis of infectious disease.

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“…34 An important feature of the retinal cycle is that it maintains an efficient supply of chromophore without competition from rods, particularly important in retinae that are numerically rod-dominated. In humans, cones constitute only 5% of the total number of photoreceptors (see Lamb 35 for an interesting commentary), so most of the chromophore produced by the RPE is consumed by rods.…”

Section: The Link Between S2 and Amentioning

confidence: 99%

Slowed Dark Adaptation in Early AMD: Dual Stimulus Reveals Scotopic and Photopic Abnormalities

Tahir

Rodrigo-Diaz

Parry

et al. 2018

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. The recovery of visual sensitivity after a photobleach in early AMD is slowed in rods but cones also may be abnormal. The purpose of this article was to test different stimulus locations to investigate cone function and its relation to rod abnormalities. METHODS.Stimuli were presented at two locations, 3.08 and 5.58, in the inferior visual field. Post photobleach dark adaptation (DA) curves from 50 early-AMD patients were compared with those from 15 healthy controls of similar age. Curves were characterized in terms of four parameters: ct, cone threshold; a, the transition point from cone to rod function; S2, the slope of the second rod-mediated component; and b, the transition from the second to the third rodmediated component.RESULTS. There were strong location effects for the healthy group and the AMD group. Cone threshold was higher for the outer compared with the inner stimulus (P ¼ 0.001), S2 was steeper for outer compared with inner (P < 0.001), a was shorter for outer (P ¼ 0.004), and b was shorter for outer than inner (P ¼ 0.002). The high variance in the patient data, particularly for a and b, explained the absence of a group*location interaction in the statistics.CONCLUSIONS. The data provide a novel perspective on abnormal cone-and rod-sensitivity recovery in early dry AMD. The comparison of pairs of DA curves from different locations highlights the involvement of cones in the underlying pathology of AMD. Dynamic measures of visual function are particularly sensitive to early AMD.

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Why rods and cones?

Cited by 84 publications

References 34 publications

AII amacrine cells in the primate fovea contribute to photopic vision

AII amacrine cells in the primate fovea contribute to photopic vision

Eyeing up the Future of the Pupillary Light Reflex in Neurodiagnostics

Slowed Dark Adaptation in Early AMD: Dual Stimulus Reveals Scotopic and Photopic Abnormalities

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